The second marine mammal park, then called an oceanarium, was established in St. Augustine, Florida in 1938. It was initially a large water tank used to exhibit marine mammals for filming underwater movies, and only became later a public attraction. Today Marineland of Florida claims to be "the world’s first oceanarium".

Between the 1970s and the 1990s, technical advances and the public's increasing interest in aquatic environments prompted a shift to large marine mammal parks with cetaceans (mostly orcas and other species of dolphin) as attractions. Within this time SeaWorld USA evolved as the most prominent chain of marine mammal parks, with operations in Orlando, Florida, San Diego, California, San Antonio, Texas, and Aurora, Ohio (which has since closed down).

Many animal welfare groups, such as the WSPA, consider keeping whales and dolphins in captivity a form of abuse. The main argument is that whales and dolphins do not have enough freedom of movement within their artificial environments. The existence of marine mammal parks is thus very controversially discussed.

Although sizable pools for whales and dolphins require an extraordinarily technical and financial expenditure and are usually nearly impossible to provide and maintain, many marine mammal parks endeavour to improve the conditions of captivity and attempt to engage in public education as well as scientific studies. For that purpose many marine mammal parks joined together in the "Alliance of Marine Mammal Parks and Aquariums", an international association dedicated to high standard of care of marine mammals. It was founded in 1987 and established offices near Washington, DC, in 1992.

In 2010, the practice of keeping animals in captivity as trained show performers was heavily criticized when a trainer was killed by an Orca Whale at SeaWorld Orlando in Florida.[3]